1. Field of the Invention
The invention relates generally to systems and methods for the communication of data and more particularly to systems and methods for producing an electrical copy of an optical data stream without altering the optical data stream.
2. Background of the Invention
With the increased computing power that is available for both commercial and private use, there is an increased demand for data transfer on a number of levels. Particularly, the emergence of the Internet and the ability of businesses and individuals to easily communicate with others around the world has created a need for greater data transfer speed, quality and capacity than ever before.
One response to the demand for increased performance in data transfers has been the development of optical data transfer systems. These systems use light instead of electrical signals to carry data from one point to another. Optical data transfer systems typically have much greater bandwidth than electrical systems of comparable size and cost and are capable of providing higher quality signals for data transmission. Ideally, a user who wishes to transport data via optical signals can transmit the data over an optical fiber which is coupled by optical routing and switching equipment to more optical fibers. The transmission of the data entirely in the form of optical signals provides for a fast, efficient and high-quality transport mechanism.
One of the problems with handling optical signals, however, is that, in conventional systems, they must be converted to electrical signals in order to process the data. For example, an optical signal which is transmitted over an optical fiber to a destination device is received and converted into an electrical signal which is then processed by the device. Similarly, when an optical signal is routed, it is normally converted from an optical signal to an electrical signal by the routing equipment, which then makes a routing decision for the signal, converts the electrical signal back into an optical signal and routes the optical signal over a selected path.
The necessity of converting an optical signal into an electrical signal for processing is problematic for a number of reasons. For instance, the process of converting the data requires a certain amount of time. While this amount of time may be small, the number of conversions which may be necessary to route the data stream from end to end may create significant latency in the data transmission. Likewise, the power which is required to perform the conversions is not insignificant.
While it is generally accepted that transmissions of optical signals from one optical component to another is faster and more efficient than the transmission of the corresponding data stream through a combination of optical and electrical components, it is nevertheless necessary to use the latter because it has not been possible to determine the content of an optical signal for processing (e.g., routing the signal) without first terminating and converting the optical signal into an electrical signal. It would therefore be desirable to provide a means to determine the content of an optical signal, and thereby enable processing of the data, without having to terminate and convert the optical signal.
One or more of the problems outlined above may be solved by the various embodiments of the invention. Broadly speaking, the invention comprises systems and methods for generating an electrical copy of an optical signal without having to terminate the optical signal, as in conventional systems. In one embodiment, an optical amplifier is configured to receive the optical signal and to allow the optical signal to pass therethrough. The optical amplifier is xe2x80x9cpumpedxe2x80x9d by applying a bias voltage across it. The energy provided by the bias voltage causes a number of atoms to become excited and to move into high-energy states, thereby creating a population inversion. Atoms which are in the high-energy states can be stimulated by light passing through the amplifier to fall into lower-energy states, resulting in the emission of photons and the collapse of the population inversion. The impedance of the optical amplifier is high when there is a population inversion and low when the population inversion collapses. Consequently, the bias current which is drawn from the power supply by the optical amplifier increases as the population inversion collapses and decreases as the population inversion is re-established, mirroring the pulses of light in the optical signal. When a resistor is placed in series with the optical amplifier, the bias current creates a voltage across the resistor which also mirrors the optical signal.
In another embodiment, an optical signal is transmitted on an optical fiber to an optical amplifier. The optical signal passes through the optical amplifier to an intermediate optical fiber. The intermediate optical fiber conveys the optical signal to a Bragg filter. The Bragg filter is configured to reduce the noise created in the optical signal by spontaneous emission of photons in the optical amplifier. The filtered optical signal emerging from the Bragg filter is then provided as an output on another optical fiber. A bias voltage is applied to the optical amplifier by a power source. A bias resistor couples the power source through the optical amplifier to ground. The bias current flows from the power source through the optical amplifier, and the bias resistor, producing a signal voltage across the resistor. This signal is amplified by an operational amplifier and provided as an output.
In another embodiment, a system comprises an optical amplifier and an optical processor. The optical amplifier is configured to be electrically biased by a power supply which generates a voltage across it. A population inversion is thereby created in the optical amplifier. The optical amplifier is configured to allow an optical signal to pass through it. As pulses of light from the optical signal pass through the optical amplifier, the population inversion collapses. The collapsing and recharging of the population inversion causes the impedance of the optical amplifier to vary, thereby causing a voltage corresponding to the optical signal to be developed across a resistor placed in series with the optical amplifier and the power supply. The optical signal and corresponding electrical signal are both passed to an optical processor. The optical processor is configured to process the electrical signal and to manipulate the optical signal based upon the results of the processing. The optical processor may be configured to manipulate the optical signal by routing it or by directly modifying one or more bits of the data stream embodied in the optical signal. The optical processor includes an optical fiber line configured to receive the optical signal from the optical amplifier and to delay it by an interval of time which is sufficient to enable the optical processor to implement the manipulation determined by the processing of the electrical signal.